There are very few people on the planet who know who the real Don Draper is. In fact, there aren't many people on the planet who know that the real Don Draper is actually dead, and the person using his name is actually a guy named Dick Whitman.

Anna Draper is one of those people.

The relationship between Anna and Dick Whitman is one of the most unique ones on television. He took Don's name after coming home from the war; she took him in, and they took care of each other. As a result, he's been able to take care of her as he's continued to carry the Draper name to New York, got married, started a family, and got a painful divorce (which was precipitated by Betty finding out the truth... more on that later). Now the Draper name is proudly on the door of an up-and-coming ad agency. They have a love for each other that's hard to describe, but easy to see.

Which is why Don's trip to Southern California on this week's 'Mad Men' (Sundays at 10PM ET on AMC) was so painful.

Yes, it was creepy as hell that Don was trying to seduce Anna's college-age niece. But that's Don; he thinks he can woo any woman, and doesn't seem to care at this point where he wields that power, as long as he can do it. Not only did she stop him short -- because she's got a head on her shoulders -- but then she turns the scene right around by telling him the bad news about Anna: that she has cancer, doesn't have much time left, and she doesn't know. "I didn't want you to leave without knowing," she told him, as a devastated look came across Don's face.

What's been surprising to me about season 4 of 'Mad Men' so far is that nothing is definite when it comes to Don or his new circumstance in life. Just when you think he has a handle on who he is, you see him come home from work so drunk he can't put the key in the lock. SCDP outwardly seems to be doing well, but inwardly is in precarious shape, both financially and emotionally. The only thing that was consistent in Don's life was his relationship with Anna, even though she was 3,000 miles away. And now that's being taken away from him.

When he confronted Anna's sister about not telling her about the cancer, you could see the true hatred of Dick/Don dripping from her words. "You have no say in the affairs of this family. You're just a man, in a room, with a checkbook. That's all." I'm sure she's always hated this arrangement Anna's been in, but tolerated it as long as Anna was being taken care of. Now that she has to take care of Anna in her last days, she wants the annoyance of Dick/Don out of all of their lives.

But give Don credit for knowing that, as much as he loves Anna, he's not family, and now's not the time to insinuate himself into her life and cause all sorts of grief. So he leaves, giving Anna a much more tearful goodbye than he's ever given anyone else in his life. Aside from his kids, Anna's pretty much the only family he has, and now he's losing her.

Jon Hamm did a really great job of showing not only the sadness Don had for Anna, but the pain in his face, showing how frustrating it was to not tell Anna about her fate, was evident.

This season is starting to feel like a year-long journey for Don, doesn't it? As with most 'Mad Men' seasons, the early episodes have been slow going, but they're showing that Don's -- or anyone's -- lives are never a simple straightforward line, and that even when you think you know who you are, something always comes along to test that notion. Which is why this season is starting to shape up into being yet another good one.